Electrical wave transmission system



Nm, 59 w29? H. J. FHSHER f WMZI ELECTRICAL WAVE TRANSMISSION SYSTEMFired May V26, 1,927

Patented Nov. 5, 192g UNET Fati,...

HAROLD J. FISHER, OF JERSEY CITY, NEWv JERSEY, .ASSIC1I\T0]3, TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK ELECTRICAL WILVE TRANSMISSION SYSTEM Application led'May 26, 1927.Serial No. 194,348.

This invention relates to electrical wave vtransmission systems andparticularly to echo suppressing circuits therefor.

In designing signaling circuits which are electrically very long, animportant problem is presented by the necessity' ot' avoiding seriousecho effects. Echo ell'ects are caused by reflections of signallingwaves which take place whenever electrical irregularities areencountered in the transmission circuits. Reflection 'of transmittedwaves occur in all practical circuits. It is only in circuits of suchlength as to require a number of repeat-ers, however, that the echoe'li'ects become serious. The fact that the circuits are electricallyvery long makes the time lag of the echoes appreciable, and at the sametime the repeaters overcome the high attentuation of the long circuitsand consequently intensify the effect of the echoes. The seriousness ofthe effect is a function both of the time lag and the volume of the,echoes relative to the direct transmission.

Various circuit arrangements known as echo Suppressors are used toavoidthese eti'ects. rlhese arrangements depend upon the fact that inall practical signaling circuits employing more than a single repeaterthere are points where the waves being transmitted in the two directionspass through separate paths. At these points the direct transmissiontakes place-through one path, while only reflected waves or echoes aretransmitted through the other. The echo suppressor is located at one ofthese points and usually consists of a relay arrangement for limitingthe transmission through the echo path without disturbing thetransmission through the main path. For satisfactory operation, it isoften required that the echo suppressor have a short operating time anda longerreleasing time. v v

In a specific preferred embodiment, this invention comprises two relayssimultaneously controlled by waves being transmitted through one of theone-way paths of a twoway transmission system. One .of therelaysoperates directly to short-circuit the second one-way transmission path.The other relay operates a third relay to put a parallel short circuiton the second one-way transmission path and simultaneously operates aretarded or slow release relay to close a holding circuit for the thirdrelay. l/Vhen the transmission ot waves over the first one-way pathceases the first two relays are released, removing the first shortcircuit from the second one-way path, while the second short circuit ismaintained for the period of time required for the slow release relay tooperate. lVith this arrangement the second one-way path isshort-circuited to limit the transmission thereover almost innnediatelyupon the initiation of transmission over the .lirst one-way circuit, andtheshort circuit is maintained for an appreciable time aftertransmission over the first circuit ceases.

In a modification of the invention, a single relay with a double set ofcontacts is employed in piace of the two simultaneously operated relays.One set of contacts operates to directly short-circuit the secondtransmission path, while the other 'set of contacts operates to directlyactuate a slow vrelease or retarded relay to put a second shortcircuiton the transmission path.

lVhile the arrangements of this invention are particularly adapted foruse as echo suppressors they may he useful in other circuits, forexample, in voice operated repeater circuits.l

The invention is-illustrated in the accompanying drawing, in which Fig.1 shows one are particularly adapted i`or'use as echo suppressor andFig'. 2 shows a modification of the invention. y

Fig. 1 shows a portion of a four wire transmission system in whichtwo-way transmission is eiiected by the use of two oppositely directedone-way transmission lines 10and 11. 'I he circuit arrangement would, ingeneral,be the same for a two-way two-element repeater circuit exceptthat in that case it 'has been found advantageous to connect.thesuppressor circuits to the input of the amplifiers.

Two one-way ampliliers 12 and 13 are associated with the lines 10 and11, respectively. The input of an amplifier-rectifier 14 is connected tothe output terminals of the amplifier 13. The operating windings of tworelays 15 anl 16 are connected in series to-the output of theamplifier-rectifier 14. Itelay 16 is of the biased type since, ingeneral, `faster 0peration is obtained with such relays. The armatureand contact of relay 16 are connected to the outputof the amplifier 12to shortcircuit` vit when the relay is operated.

'The armature an( contact of relay 15 are connected in circ Lit with one.winding 21 of a relay 17 and a battery 19. The armature andcontact ofrel y 15 are also connected in` circuit with the operating winding of aree tarded or slow release relay v18 and abattery 20. The operation ofrelay 18 supplies current to aholding winding 22 of relay 17 from thebattery 19. ,y

The 4operation of the circuit is as' follows:

When transmission is initiated overthe circuit 11, the Waves in theoutput of the amplifier 13 energize the amplifier-rectifier 14,operating the relays 15 -andf16. The operation of relay 16 immediatelyputs a short circuit on the output of the amplifier 12, thus preventingtransmission over the line 10.

.The operation of relay 15 closes a vcircuit from ground through thearmature and contact of relay15 .winding '2,1 of relay 17,- andv battery19 to ground, operating relay 17 to put a second .short circuit on the,output of the ampli-fier 12. `The-operation of relay 15 alsdcloses acircuit from ground through the armature and contact of relay 15,.operating winding* 22 ot'` relay 17, and battery 19 to ground.

winding v of Irelay 18, battery v2Ofto groueh causing the operation ofthe retardedv relay 18 which closes a circuit from ground through thearmature and contact of relay-18, holding When. transmission over theline 11 ceases,`

i a short interval the contacts of relay 17 closed due tothe circuitmaintained through v.the winding 22 bythe contact of -relay.18. Ashorttime after 'transmission over the line-- 11 has'ceased, relay`18releases, thus releasing relay 17 and removing the secondv short-circuitfrom the output of the amplifier 12.

A second echo suppressing circuit 25, similar to the circuit above*described, 'is employed for making similar short-circuiting connectionsacross the outputv of amplifierv 13 while transmission is taking placeover line 10. The connections are such that `the v'operation' of oneecho suppressor short ciry cuits the input ofthe other so that onesuppresser cannot be operated by directly transmitted waves and theother by reflected waves to prevent transmission in' either direction.

maaier Fig. 2 shows a modification of the circuit ot llig. 1 in whichtener relaysl are utilized.

lhe winding of a single relay 26 is connected to the out-put of theamplifier-rectier 14. lte-A lay 26 is provided with two sets ofcontacts. @ne vset of contacts 27 operates directly to put a shortcircuit on the line 10 and 'the other set of ycontacts 28 operates tomake a' connection from ground through the operating winding `30 of aslow release relay 29 and battery 81 to ground. The operation ot' thisrelay closes a contact 32 to place a second short circuit on the line10. Relay 29 is designed to be slow releasing so as to remain operatedfor a delinite period after relay v26 releases, thus maintaining 'theshort circuit on line 10 for an interval after transmission to amplifier14 has ceased. A similar modified echo suppressor circuit may beutilized in place of the circuit 25 for controlling the short circuit4on line 11.A

What is claimed is:

1. In a. Wave transmission system, two one- .way transmission circuits,means responsive to waves 1n one of said clrcuits for making l1connecton of low impedance acrossthe other of saidvciircuits, and meanssimultaneously responsive to waves in said one circuit for making avsecond connection' of low impedance across said' other circuit, thelast `mentioned means being arranged to remain operated for a definiteperiodjof time after transmission over said one circuit has ceased.

2. Ina wave-transmission system, twoone` way transmission circuits,means responsive to waves in one of said circuits for making aconnection =o'f low impendance across the.

other of saidcircuits, and a slow. release relayalso res onsive'to wavesin said one of saidcircuits, or making a second connection of lowimpedance across said other c1rcu1t.-

Ina wave transmission system, two one- Way transmission circuits, arelay responsive to wavesin one osaid circuits for making aconnectionof-low impedance across the other .of said circuits, a secondrelay lsimultaf neouslyresponsive'to Waves in said one circuit andasloW-release relay responsive tothe operation .of said` second relayfor making a second connection of low impedance across said'othercircuit.A

y l4. A combination 'according to the nexty preceding claim in Vwhichthe first mentioned relay andsaid' second relay are connected in series.

' In witness whereof, I hereunto subscribe my name this 24 day of May,A. D., 1927 HAROLD J.. FISHER.`

